Calls for inquiry after Murray revelations

A key crossbench senator wants an urgent inquiry after the top water bureaucrat in NSW was recorded revealing plans to abandon the Murray Darling Basin Plan.

The recording aired on the ABC's Four Corners' program shows Gavin Hanlon secretly offering to share government information with irrigation lobbyists, to help them to lobby against the water management plan.

The program also reported how billions of litres of water earmarked for the environment was being used to irrigate NSW cotton farms.

It has sparked calls from South Australia for an independent judicial inquiry into how much members of the NSW government knew.

Federal senator Nick Xenophon said what was revealed undermines the entire agreement the commonwealth and states thrashed out in 2013.

"That effectively will mean that the $13 billion of taxpayer funds committed to the Murray Darling Basin Plan will be a waste of money with this sort of undermining," he told ABC radio on Tuesday from Bali.

"There needs to be an urgent investigation as to these very serious allegations."